Adam Wagner, general manager of Barneys BP gas station on Ottawa River Road in Toledo, describes the panic he went through when his town announced a tap water ban after a high level of a toxin called microcystin was discovered. The decision changed weekend plans for residents in Ohio's fourth largest city and across four communities in southeast Michigan who connect to Toledo's Collins Park Water Treatment Plant for potable water.

Wagner, 29, has a 7-year-old son, a dog, and a girlfriend who has diabetes and needs to drink at least a gallon of water a day.

"It was like, 'What do we do?'" he says. An endless stream of questions raced through his head. For instance, how does Wagner tell his son, Kemper, not to wash his hands, only after telling him for so long that it's the right thing to do? Luckily, Wagner's father purchased some bottled water from the store soon after the ban was announced, and called to say he would drop off a supply. Wagner breathed a sigh of relief.

As it turns out, Collins may have been aware of a potential liability in Toledo's water-treatment plant: A report from the Toledo Blade a week after the incident underscored the apparent infrastructure concerns. Records obtained by the newspaper showed the state's Environmental Protection Agency warned the city's mayor of an "imminent vulnerability" in Toledo's water infrastructure — though it's unclear if it's related to the algae issue.

"I cannot underscore boldly enough the precarious condition of Toledo's drinking water system and the imminent vulnerability to failure," Ohio Environmental Protection Agency Director Craig W. Butler wrote in a June 9 letter to Mr. Collins, obtained by the Blade. Documents and emails obtained by the Blade showed the agency "had severe reservations about the plant for months leading up to the crisis," the newspaper reported.

It's not uncommon to find algae in lakes, but what causes the blooms to become harmful is a complex topic to digest and not entirely understood. Experts have been attempting to draw attention to Lake Erie's growing problem for years because, they say, it's imperative for officials and residents to begin to understand why the harmful algae blooms.

In July, scientists issued a forecast saying this year's algae blooms would be "significant," according to a story in the Sandusky Register. That forecast rang true on Aug. 2, when Toledo's water-treatment plant discovered an excess of microcystin in its supply, prompting officials to ask residents to stop using tap water immediately.

If the problem isn't tackled head-on, experts say, Lake Erie could be headed down a long and tainted path.

Besides residents in the Toledo area, the apparent lack of action on the system's infrastructure forced 30,000 residents in four communities across southeast Michigan that connect to the city's water-treatment system — Bedford Township, Luna Pier, La Salle, and Erie Township — to keep the tap off, too. Officials and experts speculated microcystin had entered the supply stream after a pea-green-colored harmful algae bloom in Lake Erie blew into the area and onto Toledo's water-intake pipe.

For three long days, scenes played out across nightly broadcast news of big-box store shelves being emptied by frantic residents hoping to score the last pallet of water. Residents were told not to drink the water, bathe in it, wash their hands, brush their teeth — nothing. They couldn't even boil the water: It wouldn't have improved the conditions of the water, officials explained, and could've increased toxic levels. The state's National Guard delivered bottled water to the area, and distribution centers were stationed across the city to deliver clean water.

Standing next to Wagner outside the Barneys gas station, assistant manager Gary Beilstein says the toxic algae bloom has been ongoing in Lake Erie for years. Except this was the first time it infiltrated Toledo's water system.

"It's a wake-up call because now ... they're going to have to start addressing the problem," says Beilstein, 66.

First, though, officials and experts have to answer the question of what happened. It may take weeks to investigate, they say, before the real cause of the problem is known.

The harmful algae bloom — spawned by a number of causes, the least of which being phosphorus-enriched stormwater runoff from nearby industrial agriculture sites — is no stranger to Ohioans. In 2011, a record-setting toxic algae covered one-sixth of Lake Erie, affecting everything from Ohio's economy to fish populations. Last fall, a small township of 2,000 just east of Toledo endured the same fate as the state's fourth largest city, with water use being suspended for a weekend. Beaches at summer hotspots like Maumee State Park are routinely closed because of harmful algae bloom; the Columbus Dispatch reports nearly 20 public lakes in recent years have been affected.